We broke the story -- Charlie has been on a mission to get Selma 86'd from the show because he believes she's been complaining about him behind his back ... trashing his work ethic.

Now, sources tell TMZ ... Charlie returned to work Monday and told producers he wants the termination process started TODAY ... or else he'll walk.

It's a big threat from Charlie -- who's set to make between $75 and $200 MILLION if he completes the 100 episode order for "Anger Management" ... depending on how it does in syndication. We're told Charlie's completed roughly half of the 100 episode order.

We're told Charlie understands that there can be complications with firing someone from a TV show ... but he wants producers to begin drawing up an exit strategy for Blair by the end of the day.

Sources connected to the production tell us ... Selma was not on set yesterday, though it's unclear if she was scheduled to work.

This morning, Blair was spotted out on a walk with her kid -- and when asked about her potential termination from "Anger" she just shook her head and replied, "I don't know anything."

We're told FX network execs are currently in talks about how to handle the situation ... but it's unclear if Blair's fate has been decided.